Database basics for getting started with Oracle databases

Concept: Database (DB,DATABASE): Bulk organization storage and operation of data Warehouse. Data Warehouse is a basic noun in the field of database, which refers to its general meaning.

Database management Systems (Dbms,database Management System): A software module that organizes and manages data in the database software

Database administrator (dba,database Administrator): Manipulating database management and maintenance personnel

Database systems (Dbs,database system): A database based application system or software system that appears relatively low frequency

relational databases (Rdb,relationship database): a database established or organized based on a relational model

relational database management System (RDBMS): It is the mainstream form of the current database

SQL language: That is, structured query Language, structured querying language. Common SQL commands are Select, INSERT, DELETE, UPDATE, CREATE, DROP

SQL is a database language that uses relational models for interacting with various databases, providing common data management and querying capabilities

SQL classification: Data definition language (ddl,data definition Language): such as Create, Alter, Drop, Truncate

Data manipulation language (Dml,data manipulation Language): Insert, Update, Delete, Merge

Data Control Language (Dcl,data controls Language): such as Grant, Revoke

Other language elements (Additional Language Elements): such as transaction control statements: Commit, Rollback, savepoint

SQL Description: Select is the most frequent and most commonly used. DBAs can use DCL for database management, and application developers rarely use it

Database overview

Management: First stage: Manual Management phase: Data not saved. Data is managed by the application, writing programs to consider data structures

Data is program-oriented and not shared. Data is not independent and varies with its logical structure and physical structure

Phase II: File Management phase: poor data sharing. Data in file form for a long time

Phase III: Database management stage: To facilitate the implementation of data sharing. Data application-oriented, not program-oriented

History: First generation: Non-relational database systems: The advent of the late 60, including the hierarchical and net-type

Second generation: Relational database System (RDBS): The 70 's in the middle of the last century. Oracle is Rdbs's representative.

The third generation: Object-relational database system (Ordbs, Oodbs): The middle of the 80 's mid-century to date. Also known as an object-oriented database system, it tries to be in the form of objects

Or the storage and manipulation of data in an object unit. So far, it has not yet launched a mature product

Category: Net-type database: A mesh data model with record types as nodes. For this intricate network of intertwined, it is very inconvenient for data retrieval.

Hierarchical database: Using hierarchical models to simulate things organized hierarchically in the real world

Relational database: The use of two-dimensional table structure to store and manage data, and specify the table and the data dependencies between the tables. Most of the mainstream databases currently used in the industry are relational databases

Current popular relational databases: Oracle (which is the industry's first name), IBMDB2, SQL Server, SyBase, Informix (its company has been acquired by IBM), etc.

Relational database uses Structured Query Language (SQL) as a bridge between client program and database server

Data modeling

Concept: In order to store the objective objects in the real world in the form of data and process them, we need to analyze, abstract and determine the structure of the data and the intrinsic relationship between the data, which is called data modeling.

Requirements: Be able to simulate the real world more realistically, easy to understand, convenient for computer to realize

Elements: Data structure: Describing the static characteristics of things

Data manipulation: Describing the dynamic nature of Things

Integrity constraints: A binding relationship between things inside and between things

The real world: the connection between things and things is objective.

Concept World: People's understanding and abstraction of objective things and their relations in the real world

In the conceptual world, the model of the real world is modeled by the user's point of view, and the resulting "conceptual data models" do not depend on specific computer systems and DBMS

Machine World: Further modeling of things in the conceptual world (linkages between entities and entities) by computer, abstracting/converting to "physical data models" related to computer/dbms

Continuation of the second: conceptual data Model (Cdm,conceptual database models): Mainly used in the conceptual design of databases

Based on entity-relationship (E-R) model, CDM abstracts objective objects in real world as entities and relationships.

In the machine world, CDM will be converted to a physical data model supported by a particular DBMS (pdm,physical Database models)

Related terms: Entities (Entity): objects that exist and can be distinguished from one another

Entity set (Entity set): A collection of identical class entities. Entities are often mixed with entity sets, generally referred to as entities. The concept of entity sets is rarely emphasized

Attributes: Describes attributes of an entity

Relationship (Relationship): The correspondence between entity sets (the interconnectedness of things in the real world)

Entity-Relationship model (E-model,entity-relationship models)

E-R model: Also known as the E-R method, which was proposed by P.p.s.chen (Chinese-American) in 1976, the method uses E-R diagram to describe the concept of the real world model

In the E-R model, the real world is composed of all the objects called entities and the relationships between them. Its three elements: the entity, the relation, the attribute

E-R diagram: namely Entity-relationship Diagram, is a practical tool to describe the concept world and build a conceptual model.

E-R diagram three elements: entity: Using a rectangular box to express

Properties: represented by ellipses and connected to entities with lines

Inter-Entity relations: In a diamond-shaped box, and connected to the relevant entities, and the connection must be marked with the type

The types of links between entities are divided into three categories, namely one-to-one relationships (1:1), one-to-many Relationships (1:n), and Many-to-many relationships (m:n).

Basic terminology of relational database

Terminology: Relationship: The entire two-dimensional table

Relationship Name: Table name

Ganso: Row data (record)

Properties: Column data (Field/component)

Property name: Column name (field name)

Primary key: The attribute group that uniquely determines the progenitor (keywords)

Fields: The range of values for a property

Relational schema: Relationship name (attribute list). such as: Student (school number, name, sex, telephone)

Constraints: Domain integrity constraints: Also known as column integrity. A constraint on the value of a field or a property

Entity integrity constraints: Also known as line integrity. Requires a unique identifier for each row in the table, which is the primary keyword

Referential integrity constraints: Also known as referential integrity. It refers to the reference between multiple tables, that is, to ensure that the data in the primary table is consistent with the data from the table

Oracle "Oracle"

Company: 1977, June founded Sdl,software Development Laboratories

1979, SDL changed its name to Rsi,relational Software INC

1983, RSI changed to Oracle

Scott is the first official employee of Oracle company except for two founders.

Is the world's largest database software and service providers, the world's second largest software provider (first is Microsoft)

Oracle is now the first in the industry, and it has a share of more than 50% in the domestic sector.

Followed by IBM's DB2, Sybase's Sybase and Microsoft's SQL Server, and so on, the MySQL application is also more extensive

Database: A globalized, cross-platform database. Oracle adheres to industry standards for data access languages, operating systems, user interfaces, and network communication protocols

Support for multi-user, high-performance transactions. Strong security control and integrity control. Support distributed database and distributed processing

The latest version is 11g,g is the grid grid. Support Grid computing, support centralization of database operation

The mainstream of current industry applications is oracle9i,i is integrated integration. It integrates the client and server side as well as other tools